Rotary transformer.



No. 682,942. I Patented Sept. l7, 19m. 5. e. LAMME.

ROTARY TRANSFORMER.

(Application filed 1.11. as, 1597.

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IJIIIM WITNESSES /NVENTOR mu/u/ By g A rrbmvn. V

UNITED STATES PATENT OFFICE.

BENJAMIN G. LAMME, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO THE WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, OF SAME PLA OE.

ROTARY TRANSFORMER.

SPECIFXCATION forming part of Letters Patent N 0. 682,942, dated September 17, 1901.

Application filed January 28, 1897. Serial No. 621,117. (No model.)

To all whom, it may concern:

Be it known that I, BENJAMIN G. LAMME, a citizen of the United States, residing in Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Rotary Transformers, (Case No. 726,) of which the following is a specification.

My invention relates to systems of electric distribution involving means for converting 2 5 conductors and commutator being shown dia grammatically. Fig. 2 is a side elevation of the rotary transformer shown in Fig. 1. Fig.

3 is a diagram illustrating the phase relation and amplitude of the magnetic fields pro- 0 duced by the armature-currents of the transformer shown in Figs. 1 and 2. Figs. 4 and 5 are respectively an end and a side elevation of a modified form of machine embodying my invention, the shaft-bearings being omit- 3 5 ted. Fig. 6 is a side elevation of another modification of my invention, and Fig. 7 is an end elevation of the rotatable parts of the machine shown in Fig. 6.

Reference being now had to Figs. 1 to 3 0 of the drawings, 1 is a multipolar field-magnet of ordinary construction, except that the pole-pieces 2 are preferably shorter and wider than those usually employed and are not provided with magnetizing-coils. In some cases coils may be altogether omitted from the fieldmagnet pole-pieces, but for machines the size and construction of which are not such as to afford the necessary circuits for induced secondary currents in the frame itself coils 2 are provided. These coils may be joined together in series, as shown, or in some cases each coil may be closed upon itself. Where the coils 2* are joined together in series, as indicated in Fig. 1, it will usually be advisable to provide a switch 2 for opening and closing the circuit. This switch may also embody a variable resistance 2. The pole-pieces 2 are preferably laminated, as is usual, and cast into the body or frame of the field-magnet. The armature 3, which is shown diagrammatically, is preferably of the usual ironclad type-that is, provided with deep slots or grooves in which the coils are located-the winding being of the usual direct-currentgenerator closed-coil type, and connected at one end to the segments of commutator-cylinder 4, on which bear brushes 5, and at the other end to collecting-rings 6, on which bear brushes 7. In the construction shown four rings and four brushes are employed, which indicates that the machine is constructed for the transformation of two-phase alternating currents, although it is to be understood that the machine may be constructed for the transformation of currents of a different number of phases,- if desired.

If multiphase currents are applied to the armature-winding of the machine above described at the proper points, magnetic fields or poles shifting or rotating about the axis are produced, the armature-windin g forming the magnetizing-coils. If the armature be rotated in a direction opposite to that of the shifting magnetic field and at an equal rate of speed, the poles or fields will remain fixed in space, as in an ordinary machine with field-magnetscarrying magnetizing-coils. If the brushes be located on the commutatorpoles, they will deliver direct current. In order to keep the magnetizing-current small, there must be a good magnetic path outside of the armature-body; This is provided in the form illustrated by the cast-iron frame having the laminated pole-pieces. The spaces 1 between adjacent pole-pieces obviously constitute slots or grooves in the field-magnet frame taken as a whole, this construction beneutral points to facilitate commutation of the currents generated or transformed in the armature of the machine. If the armaturecylinder in positions midway between the ing employed in order to provide or insure granted March 1, 1898.

coils are of the same width as the pitch, the magnetic field due to one phase is pointed, while the resultant of the two phases is flat topped, the areas of the two being equal, but the heights being different. Consequently the total induction per pole is constant, but the maximum resultant induction is materially diiferent from the maximum induction the winding. The direct current will also set up a magnetic field which is a maximum at the point where the direct-current brushes are in contact. The direct-current brushes should commutate the coils at the edge of the field which generates the direct-current electromotive force, and consequently the field due to the magnetizing alternating current should be shifted to a ninety-degree position with respect to the field due to the direct current in order to give proper commutation. This is actually the condition in the machine, for the magnetizing alternating current lags about ninety degrees behind the alternating-current electromotive force, as is evidenced by the fact that the apparent .magnetizing energy is much greater than the true watts when the machine is running without load. As the load comes on, the alternating current, which is represented by an equivalent direct current, is in phase with the electromotive force applied, and therefore at ninety degrees to the magnetizing-current.

This useful alternating current will also set up a field. We have then three magnetic fields set up, two of which are one hundred and eighty degrees from each other and the third at ninety degrees from each of the others. The two at one hundred and eighty degrees are those due, respectively, to the useful alternating current and the direct current. These are opposite and approximately equal in value, and they therefore neutralize each other. The field set up by the useful alternating current is represented in Fig. 3 by the line a, that by the direct current by the line b, and that by the magnetizing alternating current by the line a. As the direct current and the useful alternating currents are Very nearly equal in magnetizing power and oppose each other, the only field in the machine is that due to the magnetizing-current. This may be much less than would be given by either of the other two fields, or, in other words, the magnetizing-current in a properly-designed machine of this type may be made much smaller than the useful current 'the useful alternating current is about thirtyeight per cent. for two phases and about sixty per cent. for three phases of the loss in a direct-cu rrent machine. To this must be added the loss due to the magnetizing-current, which is usually small.

It has been found that if the keeper or outer ring is in the form of a cast yoke providedv witheither cast or laminated poles or projections, as indicated in the drawings, the armature will run at the proper speed without any other devices for driving. This is similar to making the external ring with notches to reduce the local field around the commutated coils, as shown in Fig. 4 and hereinafter described. As has alreadybeen stated in substance, coils located on the pole-pieces and short-circuited on themselves are useful and desirable in machines the yokes or frames of which are laminated or are so small in cross-section that they do not afford proper circuits for induced secondary currents.

A machine like that described is independent of wave form and may therefore be run in connection with any type of alternatingcurrent generator. Such a machine will run steadily under any condition, whereas a rotary transformer of the ordinary form is sensitive to line drop, adjustment of figld strength,&c. Several machines of the type described may be run from a common set of bus-bars without interfering with the operation of each other in any way. ciency of such machines is high on account of there being no field losses, and the amount of copper employed is only about one-fourth of that necessary in the ordinary form of rotary transformer.

In Figs. 4 and 5 I have shown a machine having an armature, commutator, collecting rings, and brushes like the corresponding parts shown in Figs. 1 and 2. of machine, however, I employ a ring or keeper 1*, built up of laminae, provided with slots or "grooves 1 corresponding in number and position to the spaces .or slots between the pole-pieces 2 of the machine. in Figs. 1 and 2.) Since these slots or spaces are intended to provide neutral points for In this form (Shown commutating purposes, it will be understood as in the forms already described. Inasmuch as the keeper rotates with the armature,

grooves or slots will serve no useful purpose and need not therefore be provided. The op eration of this modification also differs from that of each of the other forms shown and described in that the machine is not self-propolling.

I desire it to be understood that the details of my invention may be varied from what is shown and described without departing from its spirit and scope.

I claim as my invention 1. In a rotary transformer for converting multiphase alternating currents into direct currents, the combination with a member having magnetizing-coils, of means for supplying multiphase currents to said coils and means for taking direct currents therefrom, and a magnetizable member having laminated projections separated by air-spaces and located adjacent to said coil-wound member but having no magnetizing-coils, whereby the machine runs as a motor and delivers a smooth, direct current.

2. In a rotary transformer, the combination with two concentrically-arranged and relatively rotatable magnetizable members only one of which is provided with a magnetizingwinding, of means for supplying multiphase alternating currents to said winding and a commutator for taking direct currents therefrom, the other member being provided with grooves or slots corresponding in number and position to the commutator-brushes.

3. Means for transforming alternating into continuous currents, comprising a slotted cylindrical core, a commutator, collecting-rings and brushes, a closed-coil winding located in the slots of said core and connected to the commutator-segments and collecting-rings, and a slotted magnetizable member without magnetizing coils surrounding said cylindrical core and in close proximity thereto.

4. Means for transforming multiphase alternating currents into continuous currents, comprising a rotatable core provided with a single winding connected to both the alternating and the continuous current circuits .and a magnetizable member without magnetizing-coils in close proximity to said core and its winding.

5. In a rotary transformer for converting multiphase alternating currents into continphase currents to said winding and means 5 5 for taking direct current therefrom, in combination witha field-magnet havinginwardlyprojecting laminated pole pieces without magnetizing-coils, whereby the counter electromotive force of the machine is dependent entirely upon the magnetic field set up by said armature, and runs as a motor.

6. A rectifier for phase-diifering alternate currents consisting of a cylindrical core having a continuous winding, said winding being connected to the source of phase-differing a1- ternate currents at angular intervals corresponding to the phase differences of said currents, and further connected at regular intervals to segments of a commutator, a keeper traversed solely by the flux due to said phasediffering currents and brushes connected with the work-circuit and bearing upon said commutator and means for maintaining said brushes continuously in contact with the points of maximum potential in said winding, substantially as described.

7. In a rectifier for alternating currents of diiferent phase, a cylindrical core having continuous winding, said winding being connected to a source of phase-differing alternating currents at regular intervals corresponding to the phase difference of said currents, and further connected at regular intervals to segments of a commutator and brushes connected with the work-circuit bearing upon said commutator in combination with a keeper having polar projections as to which said cylindrical core is relatively revoluble, said keeper being energized only from the fiux of the currents passing through the winding on said cylindrical core, substantially as described.

In testimony whereof Ihave hereunto subscribed my name this 26th day of January, A. D. 1897.

BENJ. G. LAMME.

Witnesses:

WESLEY G. CARR, HUBERT G. TENER. 

